The present invention relates to magnetic recording and playing back apparatuses, and more particularly it relates to video tape recorders (VTR) which can record and playback information with a tape packed in a cassette equipped with an ID board.
In recent years, digital VTRs have prevailed not only in professional uses but also in consumers"" households, and the certain consumers frequently use digital VTRs to their entertainment. This digital VTR employs a digital video cassette and digital video mini-cassette in accordance with a relevant standard. The cassette rear plate where a label is pasted has an ID board including four terminals.
A conventional magnetic recording and playing back apparatus is described hereinafter.
In FIG. 3, mechanism 311 is constructed as follows: Rotary-head-drum 321 includes a magnetic head (not shown) for recording or playing back information such as audio and video signals. Drum 321 spins at a given rotating speed. Cassette housing 327 houses a magnetic tape such as a metal evaporated tape (ME tape) or a metal particle tape (MP tape). Housing 327 can also houses a cleaning tape.
Supply reel 317 and take-up reel 319 transport the tape packed in the cassette housing 327. When the housing 327 is loaded into a VTR, loading posts 313 move from positions 315 to the marked positions thereby pulling the tape out of the housing 327 and winding the tape around drum 321.
Loading controller 323 instructs loading posts 313 to move the tape. Reel controller 325 instructs supply reel 317 and take-up reel 319 to spin, and at the same time, it also strengthens or moderates a back tension applied to the tape. Controller 329 instructs loading controller 323 to load the cassette tape into the VTR, or instructs reel controller 325 to spin the reel.
An operation of the conventional VTR thus constructed is described hereinafter.
When cassette housing 327 is loaded to mechanism 311 of the VTR, a motor (not shown) coupled to rotary-head-drum 321 is driven, whereby drum 321 starts to spin at a given rotating speed. Reel controller 325 applies a given tape tension (back tension) to the tape, and loading controller 323 instructs posts 313 to pull the tape from locations 315 and wind the tape around drum 321 covering a given angle on drum 321.
When a cleaning tape is loaded, posts 313 sometimes fail to pull the cleaning tape out of housing 327, or the tape loading is not completed because drum 321 is prevented from being spun. This troublesome case is described hereinafter. In this case, controller 329 firstly instructs loading controller 323 to unload the tape in order to avoid damaging the tape. Loading controller 323 follows the instruction and retracts posts 313 to positions 315, thereby restoring the tape into the cassette.
However, the conventional construction described above applies a given back tension to a tape regardless of tape characteristics, so that a difference between the frictional coefficients of different kinds of tapes causes the troubles described above. As a result, the heads of the VTR are not cleaned anymore.
A reason why the cleaning tape cannot be pulled out of the cassette is this: the back tension applied to the cleaning tape by reel controller 325 at the loading is stronger than a force of posts 313 pulling out the tape by loading controller 323. When a back tension is applied by reel controller 325 based on the ME tape or MP tape having a low surface frictional coefficient, the cleaning tape of which frictional coefficient is high encounters resistance at both the reels in loading. As a result, the cleaning tape cannot be smoothly pulled out of reels 317 and 319. The resistance and the back tension eventually halt the loading operation of posts 313.
A reason why drum 321 halts to spin is also a back tension applied to the cleaning tape and resistance due to high frictional coefficient of the cleaning tape. These two factors prevent drum 321 from spinning when the cleaning tape winds around drum 321, and eventually halt drum 321 to spin.
The present invention addresses the problems discussed above, and aims to provide a magnetic recording and playing back apparatus having a function to determine a kind of tape and to change a back tension applied to a tape responsive to the kind of tape.
The magnetic recording and playing back apparatus of the present invention can accommodate a cassette on which an ID board is equipped, and from the ID board characteristics of the tape packed in the cassette can be detected. The apparatus comprises the following elements:
(a) a loading controller (a first controller) for instructing a mechanism to pull a tape out of a cassette;
(b) a reel controller (a second controller) for instructing a reel to spin so that a back tension is applied to the tape when the tape is loaded;
(c) an ID board detector for determining a kind of tape based on information from the ID board; and
(d) a third controller for varying the back tension to be applied by the reel controller to the tape responsive to the kind of tape determined by the ID board detector.
This construction allows the magnetic recording and playing back apparatus to accommodate a cassette tape regardless of the tape characteristics.